Boom locking apparatus for a back hoe



Feb. 17,

J. P. WAITE' 2,873,871

BOOM LOCKING APPARATUS FOR A BACK HOE Filed July 5, 1955 -w 51mm; Z7 4 Z3 4 3 INVEIYTOR.

/ John F. Wazte miiawtk ATTORNEYS.

United States Pate-1 I 2,873,871 BQQMLQCKING ABPARATUSFOR A BACK HQE' JohirP. Waite, Milwaukee,,Wis., assignor'to J. P. Waite, Inc.,.Milwaukee-,1Wis., a corporation ofiWisconsrn ApplicatiouJuly 5, 19.55 S.e rial No. 519;986

4-Ci!ims. (Cl. 214-138) respect to. the boom to provide a digging. and dumping action forthedipper. a

If during; digging, the. dipper. encounters ahard material which is difiicultto. penetrate, theboom tends} to. pivot. upwardly rather than the dipper. digging. into! the material because the combined weight of. the-dipper and the. boom is, not, sufficient to cause penetration of the, hardmaterialby thedipper.

Thefpresent invention s. directed to an. apparatus as.- sociated with the boom for. bringing the weight. oi the cab. supporting structure. to bear 011-1116.:(11119611 to. increase theforce off penetrationjof, the dipper into the material to be. excavated. According. to the, invention a closed hydraulic system is provided. Whichjncludes. a cylinderyhavinga ram freely slidable thereinlarid acom duit which providesfcommunication betweenthe. opposite ends of the cylinder; Ihecylinder. is; c o nnected'to either the boom orisupporting structure and. the ram is connected to the other. Asthe boomispivotedwith. re spect to the supporting structure, the ramis movedwithin the cylinder and. the. fluidflowsthrough the/system with the fluid being displaced from, one end of. the. cylin der and. passing. through the conduit" to the. other end of the cylinder. 1

look; the boonpwith, respect to. the: supporting structure; a valve; is provideddn the; conduit and; by v closing the. valve. the. flow orfluid thro gh.t e-.. 0$ d ys is cutoff... Thisaprevents:themove neut-ofithe;ram;within the. cylinder and locks.- .the:- booniz with. respect: to: :the supporting-structure With the boom locked in' position with respect; to the'supporting member the-boom and supporting member-arein effect an integral structure and the weight of the suppoirting member is brought to'bear on the dipper as the-dippenpenetrates into the materialto'-;b e excavated: This tends topreventithe' booni from ha'rd 'material's. v t The present invention, provides, a. simple. and; inex pensive meansfof bringing; the: weight oflthe supporting structure to hear on the--bnomjtq jncrcase thel. foree exerted; during digging, The apparatus.- of this invention can be. readily adapted to conventional, back hoe: or; crane f constructions without; any: major alterations.- or the." parts' or elements of the-hoe; r

The drawingsdllustrate the best mode presently corn tem'plate'dof carrying-outthe-presentinvention.

pi a up a db o .r i ns. en ths rn e at -rs Patented Feb. 17, 1959 In. the drawings: Figure 1 is .;a digrammatic,side elevation of a back hoe employing. the present. invention;

' Fig 2, is a fragmentary enlarged side elevation with parts, broken away in; section and showing; the hydraulicv system for locking. the boom in position with relation 1 to the supporting structure;

, Fig; 3. is a; view similar to Fig. 2 with the boom being in,a lowered-position; and Fig. 4 is a, top planview of the structure shown in Fig. 2.

r The drawings illustrate a power operated back hoe or. drag shovel. having a cab '1- which houses the drive. mechanism and is rotatable. on crawlers or treads 2.

A. boom 3 is pivotally connected tov a pair of lugs 4. which extend upwardly from the floor of the cab. A

' dipper: stick 5 is pivotally secured to the outer end of the boom 3 and the dipper stick carries a dipper 6 which is adapted to penetrate and dig into the material to be excavated.

The dipper 6 and dipper stick 5 are pivoted about i boom 3 by acable 7 which is secured to cabledrum 8.

Cable 7 passes over. sheaves 9 and 10, which are secured to boom 3, and sheave 11- which is secured to the forward. edge. of. the dipper. The cable 7 is dead-ended on the boom as indicated by 12. With this sheaving arrangement, the dipper is drawn. inwardly toward the boom ascable. 7 is retrieved and moves away from the boomas the cable ,7. is. let. out.

The boom. 3 is. raised andlowered. by a. conventional sheaving. arrangement in which a cable. 13, which is secured to cable drum 14, passesover sheaves 15 and 1.6; and. is dead-ended on arms. 17: which. are pivotally attached to the upper end of dipper stick Sand supports the, sheave 1.6. Sheave, 15 is rotatably secured to braces 18:. which extend upwardly from cab 1.. .Byretrieving cable 13, sheavelfiis moved toward sheave 15 thereby pivoting boom 3 upwardly about the. forward portion of the cab, whileletting out. cable 13 serves to. pivot boom 3. downwardly with respect to the cab 1.

V During the. digging operation the. dipper 6 may frequently encounter hard rnaterials, which. are difficult to penetrate, andthev boom thereby tends to pivotupwardly rather. than, the dipper digging. into the material. be.-. causethe combined. weight. of the boom and dipper is not sufiicient to cause penetration of the, material by thedipper. 'lozoverc ornev this difiiculty', means arepro' vided' toflprevent' pivotal movement of the boom with respect. to the cab or supporting .structure so thatnthe weight of the cab 1 and machinery and; treads 2 will be brought to. bear on the dipper. to thereby increase: the force of penetration exerted by the dipper. is accomplishedby pivotally attaching a; cylinder. or reservoir 7 i ,theI-lowenend. 0 rod 22,.ea'tending downwardly, beyond thepiston. 21; s-lapproximately equal to thelengthxofl the; upper portion .o f the rod extendingupwardly beyond. the piston, the effective,v volumeof. the, cylinder. oneither sideof'the piston, when the piston is in .thec'enterof the I cylind'er;,is.the same.

Toprovidea closed hydraulic system .for the hydraulic fluid; 'a conduit 24 is connected between fittings 25' and26 which are secured within openings'in the opposite endf portions ofcylinder19. The" conduit "24 esta'ba lishes communication between the opposite ends of the cylinder, and as the boom 3 is pivoted with respect to the cab 1, the piston 21 moves within the cylinder to discharge fluid from one end of the cylinder through conduit 24 to the opposite end of the cylinder.

For example, as the boom 3 is lowered or pivoted downwardly with respect to the cab, the piston 21 is moved upwardly, thereby forcing fluid from the upper end of cylinder 19 downwardly through conduit 24 to the lower end of the cylinder. When the boom 3 is raised, the piston 21 moves downwardly within cylinder, 19 forcing fluid from the lower end of the cylinder through conduit 24 to the upper end thereof. Due to thefact that the piston rod extends through both ends of cylinder 19, the volume of fluid displaced from one end is equal to the increased volume available for fluid at the other end of the cylinder and thus the piston can travel to the ends of the cylinder without interference.

To cut off the flow of fluid within the closed hydraulic system and thereby prevent relative pivotal movement between the boom 3 and cab 1, a valve 27 is disposed in the conduit 24. Valve 27 may either be manually or automatically operated and serves to prevent the flow of fluid through the conduitvand thereby prevent movement of piston 21 within the cylinder 19.

In operation of the present apparatus the boom 3 is lowered by letting out cable 13 until the dipper has been lowered to the desired position. The valve 27 is .then closed to prevent flow of fluid through the closed, hydraulic system and thereby prevent relative pivotal movement between the boom 3 and the cab 1. The dipper is then actuated by retrieving cable 7 and penetrates into the material to be excavated. If the dipper engages hard material, the weight of the dipper 6, boom '3, cab 1 and treads 2 will be brought to bear on the dipper to increase the force of penetration. This added weight, which in effect acts through the dipper, tends to prevent the boom from pivoting upwardly and will increase the digging force of the apparatus.

While the present description is directed to the cylinder 19 being connected to the cab 1 and piston rod 22 connected to the boom 3, it is contemplated that the cylinder can be connected to the boom and the piston rod to the supporting structure. Similarly, the cylinder and piston rod could interconnect the supporting structure and the lower surface of the boom. In this event, the action of the piston rod would be opposite to that described above.

The present invention provides a simple apparatus for increasing the force exerted by the dipper during digging. The apparatus may readily be adapted for use with convention-type back hoes, cranes, or other apparatus having a boom which pivots relative to the supporting structure.

Various modes of carrying out the invention are contemplated as withinthe scope of the following claims particularly pointing, out and distinctly claiming the subject matter which is regarded as the invention.

I claim: p 1. In a power operated back hoe, a supporting structure, a boom pivotally. attached to the supporting structure and adapted to carry a dipper, a cylinder to contain a hydraulic fluid and pivotally connected to the supporting structure a piston freely slidable within. said cylinder, a piston rod secured to the piston and extending through opposite ends'of the cylinder and having one end thereof pivotally connected to the booth, at conduitextending externally of the cylinder providing communication between the ends of the cylinder with the fluid being displaced from one end of the cylinder by said piston and being free to pass through the conduit to the other end of the cylinder as the piston moves within the cylinder, separate means for pivoting the boom with respect to the supporting structure with the piston being moved within the cylinder as the boom is pivoted, and valve means disposed in the conduit to shut off the flow of fluid therethrough and lock the boom in a given position with respect to the supporting structure and bring the weight of the supporting structure to bear on the dipper as said dipper penetrates into the material to be excavated.

2. In a power operated apparatus, a supporting mem her, a boom member pivotally attached to said supporting member, a closed hydraulic system including a reservoir connected to one of said members and conduit means providing communication between opposite end portions of said reservoir, a hydraulic fluid disposed within said reservoir, a piston rod disposed through aligned openings in opposite ends of said reservoir and connected to the other of said members, a piston secured to the central portion of said rod and slidable within said reservoir, separate means for pivoting the boom member with respect to the supporting member with said piston adapted to move within said reservoir in accordance with pivotal movement of said boom mem' her-and displace a quantity of said fluid from one end portion of said reservoir through said conduit means to the other end portion of said reservoir, and means associated with said hydraulic system for cutting off the flow of said fluid through said system to lock the boom member with respect to saidsupporting member and prevent pivotal movement therebetween.

3. In a power operated excavator, a plurality of longitudinally spaced ground supports, a frame structure supported by said ground supports, a boom structure pivotally connected to the frame structure for movement in a vertical plane, a digging implement pivotally connected to the boom structure for movement in a vertical plane and for ground contact forwardly of the ground supports, power means to pivot the boom structure, power means to pivot the digging implement, a cylinder containing a fluid and pivotally connected to one of said structures, a piston freely slidable within said cylinder, a piston rod connected to the piston and extending through an end of the cylinder and having the outer end thereof pivotally connected to the other of said structures,rconducting means providing communicationbetween the opposite end portions'of said cylinder with the fluid being free to flow from one end portion of the cylinder through said conducting meansto the opposite end portion of the cylinder as the piston moves within the cylinder, said cylinder and said piston being separated from said first named power means and said piston being adapted to move relative to the cylinder as the boom structure is pivoted by said first named power means, and normally open valve means associated with said conducting means to normally permit free flow of fluid through said conducting means during pivotal movement of said boom structure and to restrict the flow of fluid through said conducting means when closed and lock the boom structure with respect to the frame structure and prevent pivotal movement therebetween, whereby when the digging implement is pivoted relative to the boom structure to produce an upward reaction of the ground on the digging implement, such pivoting will tend to elevate the boom structure and the forward ground supports to transfer weight from said forward ground supports to the digging implement. V I

4. In a power operated excavator, a supporting structure, a boom'structure pivotally connected to the supporting structure for movement in a vertical plane, a digging implement pivotally connected to the boom structure for movement in ave'rtical plane, power means for pivoting the boom structure and for pivoting the digging implement, a hydraulic system separate from said power means and including a cylinder containinga hydraulic fluid and a piston freely slidable within said cylinder and having a piston rod extending through an end of said p 'll,

cylinder, said cylinder being pivotally connected to one of said structures and said piston rod being pivotally connected to the other of said structures, and said hydraulic system having conducting rn'eans providing communication between opposite end portions of said cylinder with the fluid being free to flow from one end portion of the cylinder through said conducting means to the opposite end portion of the cylinder as the piston moves within the cylinder, said piston being adapted to move relative to the cylinder as the boom structure is pivoted, valve means associated with said conducting means to restrict the flow of fluid therethrough and lock the boom structure with respect to the supporting structure and prevent pivotal movement therebetween, and means associated with the hydraulic system to compensate for the volumetric displacement of the piston rod in the cylinder, where- References Cited in the file of this patent UNITED STATES PATENTS 756,831 Clarke Apr. 12, 1904 2,228,865 Bird Ian. 14, 1941 2,303,852 Linn Dec. 1, 1942 2,553,912 Gervais May 22, 1951 2,627,985 Sathre et a1. Feb. 10, 1953 2,718,312 Pilch Sept. 20, 1955 

